Information Technology Reference
In-Depth Information
For content uncontrollable applications, their data trac consumptions are
largely depend on the actual contents they have accessed, we can not control it,
leading the diculty of comparative experiment control, and making the result
unfair. So in this paper, we choose four kinds of content controllable applications
including web browsers, maps, online music players and video calls to evaluate.
3 Evaluation Framework
We need a framework to help us explore the 3G charging system and evaluate
smart phone applications. In order to meet all kinds of requirements including
future needs, this framework should be running on smart phone and be able to
record every detail information including protocol header of each layer, the con-
tent and the time of send/receive for each packet. As far as we know, there is no
such framework to accomplish these tasks. However, this framework is very nec-
essary. since compared with laptops and netbooks, the transmission power and
signal strength of smart phones is quite different (generally weaker), a framework
can accurately reflect the actual experience of the user only when it is running
on the phone. It can bring considerable convenience for the test and evaluation
process when it can get detail information of each packet. And it can also reduce
manual operation thus making the test and evaluation process more ecient.
Next, we will introduce TraSt, a trac statistics framework that can meets the
requirements. It is an open application framework. Which can get detailed infor-
mation of each packet, and provide interfaces for the test and evaluation process.
3.1 Challenges
It is dicult to implement such a framework. Although Android is an open source
platform and its kernel is Linux, a lot of tools that can be used on Linux cannot
be directly ported to Android because of the difference of system architecture.
The statistical result should be displayed on UI, so we should implement the
framework at the Application Layer. Application Layer's program can only get
the System Permissions (lower than the Root Privileges). But the Root Privi-
leges is needed to capture packets. So the best solution is a combination of the
Application Layer and Libraries or Linux Kernel Layer. This also involves the
Android NDK development [2], which needs cross compiling.
3.2 Framework
TheframeworkofTraStisdepictedinFigure2.WecompiledaTcpdump[5]
which is able to run on Android. And cross compiled the C part of Jnetpcap [3]
and libpcap [5] source code with NDK to build a shared library libjnetpcap.so.
This shared library will run on Android Libraries Layer. When TraSt starts
running, it will call Tcpdump to capture packet and save it to a .pcap file.
Then the libjnetpcap.so will read the .pcap file, get the detailed information of
each packet and send them to the Application Layer for further processing. The
